Manufacture of foundry molds



Patented July 11 1933 JEAN BAPTISTIL DURAND, OF MARSEILLE, FRANCE MANUFACTURE OF FOUNDRY MOLDS No Drawing. Application filed April 4, 1930, Serial No. 441,709, and in Germany April 4, 1829.

In the American patent application Ser. No. 394,387, filed September 21st, 1929, it has been proposed to utilize a sand composition consisting in an agglomeration of sand,

a hydraulic binder and water in such a quantity as necessary to conserve a subhydrated state.

One object of the present invention is to utilize in the process of myaforesaid application, in place of the natural sands therein described, artificial sands of any composition which have the property of becoming set when mixed with ahydraulic cement, and have also the refractory property necessary for resisting the cast molten metal. Another object of the present invention is to utilize as artificial sands for the purpose described above the material obtained by crushing the old molds made by the process described in my aforesaid application, Serial Number 394,387. The mixtures whereof those molds are made can be re-used to great advantage in the making of other molds because: (I) the binding agent forms a body much less resistant than if sufficient water had been used to cause the mixture to set, and hence the body is readily reduced b crushing to the fineness of sand; and (2 the binding agent, being sub-hydrated, has.

absorb more water, while still maintaining such a state of dryness that there is no need to stove dry the mold.

In thus re-using the material whereof molds have been made according to the invention of my said prior application, it is advantageous to use an additional quantity of binder; although it is possible to make a mold by the addition only of a proper quantity of water.

There are also to be considered as artificial sands for the purpose of this invention, the materials obtained by crushing the materials as coal, cokes, lignite, talc, baryta, asbestos etc. all substances sometimes useful for obtaining contact surfaces with the molten metal. It results from this, that the molding process in question may be extended to the preparation and application of special layers intended for surface contact still an affinity for water and can therefore and with the poured metal. The process may thus be used for making special layers forming contact surfaces with the molten metals by thin layers or for making the whole mass of the prepared mold.

This action of the surface is intended, for example, to produce on the castings a peculiar surface aspect or a determined quality of the castings over a certain thickness.

In particular in casting iron objects the layer directly in contact with the metal may be composed of a mixture of sands rich in carbon, such as coke, with cement, so as to offer to the molten metal a surface not onl refractory but also resistant to decompos1-' tion, or of a composition different from that obtained by silicious or aluminous sands or dinarily used. The application of the process can lead in this case to castings having a surface without scorifications and easy to free from sand.

The surfaces thus prepared need not generally be given a coat of paint which renders the manufacture of molds very simple. In this case as it is not necessary to appl a wash the layer forming the contact sur ace I may be less subhydrated than the composi tion constituting the mold provided that the latter is sufiiciently subhydrated.

The surface layers of the mold should contain such a quantity of binding agent and materials having such properties as will give in each case the special results desired. For example, the addition of carbon, such as coke, results in iron castings having nonscorified surfaces; the addition of coal non freed from gas results in obtaining crackled surfaces with an ornamental aspect; the addition of talc baryta, asbestos, or magnesia gives very smooth surfaces.

In particular, where a protection layer is used the sand constituting thebacking mass of the molds may be made of a natural or artificial sand of any kind. Even a sand of coarse grains may be used, the effect being to increase the porosity of the mold.

I-claim:

'1. In a process for manufacturing molds cores for foundries subhydrating an ag- 0 glomeration of sand of any species and a hydraulic binder, molding the said ag lomeration, and coating the interior of t e mold with a. facing layer constituted by a mixture of carbon, cement and water.

5 2. In a rocess for manufacturing molds and cores or foundries, subhydrating a first agglomeration of sand of any species and a h raulic binder, subhydrating a second aggomeration of sand of any species and a ydraulic binder to a lower degree than the first agglomeration, and making the external parts of the walls ofthe mold and the integral parts of the walls of the core with the first agglomeration, and the internal parts of the walls of the mold and the external parts of the walls of the core with the second agglomeration.

3. The process of forming a composition for foundry molds by mixing together artificial sands having the pro erties of becoming set when mixed with hydraulic cement and of resisting cast molten metal and a hydraulic binder with water in such quantity as to conserve a subhydrated state.

4. The process of formin a composition for foundry molds by crushmg the material constituting molds made of subhydrated agglomerate of sand and hydraulic binder and adding thereto water in such quantity only as to conserve a subhydrated state.

5. In a process such as specified in claim 4, the addition of a further quantity of binder.

In testimony whereof, I have signed my name to this specification.

JEAN BAPTISTEDURAND. 

